JPS6185480A - Storage stable polyurethane resin powder paint - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Around 1970, the rapid development of the new powder era began. In this case, for example, German patent application publication cylinder 1.9
57.485 and German Patent No. 2.127.839
PUs based on isophorone diisocyanate-polyol adducts blocked with 1-caprolactam and polyester polyols, as disclosed in No.
R-powder is a problem. 1-caprolactam-blocked inphoron diincyane) (IPDI
) melts at 55-55°C.

Blocked IPDI due to its low melting point
Powders made from agglomerate during storage. To increase the melting point, IPDI was subjected to a chain extension reaction with a polyol (NCO:
0H=2:1). German Patent No. 2,10
No. 5,777 discloses polyols such as trimethylolpropane, 2,2.4 as chain extenders for IPDI.
1,6-trimethylhexanediol and diethylene glycol are mentioned; German Patent Application No. 2,542,191 describes mixtures of di- and tri-functional polyols.

This 1-rPD blocked by caprolactam
The paint coatings produced with I-polyicanate adducts during heating are characterized by good flow properties, good chemical resistance and good paint properties. A decisive disadvantage of these polycrethane powder coatings is their high curing temperature. This is approximately 200°C.

Attempts have been made to reduce this high curing temperature of FOR-powder coatings. To the German patent application publication tube 004, 876
No. 2.10 to 777 discloses that blocked IPDI-adducts with higher reactivity compared to the PUR-powder hardeners described in German Patent No. 2.10 to 777 have a ) I is obtained by reacting IPDI with a polyol such that at least 53 and at most 8 NCO equivalents are reacted and the free NCO groups are then blocked.

German Patent Applications No. 2,755,497 and No. 2,842,641 are characterized in that they contain as curing agent an IPDI-adduct containing an in-7 annulate group blocked with a-caprolactam. Certain reactive FUR-powders are disclosed.

FOR as stated in the claims of these specifications
- The curing temperature of the powder is at least 170°C.

NGO- blocked with cyclic amidines as curing agent
By using IPDI or IPDI-polyol adducts (NCO:0H=2:1), it was possible to further lower the curing temperature of the PUR powder (German Patent Application No. 2.744, 721). No. Specification). The cured powder coating film shows a clear yellowing in any case.

There is a great deal of interest in FUR powder hardeners, which make it possible to produce weather-resistant, non-discoloring powder coatings even at temperatures below 170 DEG C.

From German patent application publication number 4221.558,
The use of secondary amines as blocking agents for isocyanates and also for the field of solvent-containing coatings is known. The use of amines for this purpose is problematic, since in both cases some amines remain in the paint and lead to discoloration (German Patent Application No. 42
21゜558, page 8, line 34 and German Patent Application Publication No. 3.039.824, page 6, line 1
(See line 9).

The suitability of amines as blocking agents in the field of solvent-containing coatings was unexpected. This is evident from the fact that the amine can be almost quantitatively removed together with the solvent.

Surprisingly, the inventors have found that it is almost universally possible to use secondary amines also in powder coatings, without discoloration under baking, overbaking or dew conditions. This was unexpected even for those skilled in the art. This is because, as is well known, many T4 blocking agents remain in the cured powder coatings and, due to amine-induced discoloration during baking, inevitably result in unusable products. That's because there wasn't.

Unsuitable amines include, for example, diisopropylamine, which in the field of powder coatings forms considerable foams due to its high reactivity.

By using this secondary amine, IPDI-based FOR-powder curing without a chain extension step has the advantageous properties of the hardeners mentioned at the beginning, but with increased reactivity than the hardeners. agent is easily delivered.

The subject of the invention is a polyol and a blocked isophorone diisocyanate (IPDI).
In storage-stable polyurethane resin powder coatings that cure at temperatures below 0°C, IPDI is expressed by a general formula having a boiling point of at least 150°C [wherein R and R/ are an alkyl group and this alkyl group is N
is always substituted in the α-position with the same or different substituents from the group of optionally substituted cycloalkyl groups, aralkyl groups, R and xl in total are at least 9 carbon atoms and optionally R and RI may form a common ring with at least 3 carbon atoms, these carbon atoms optionally being heteroatoms. interrupted and possibly replaced by (N, o)]
The above-mentioned polyurethane resin powder coating is characterized in that it is reacted with a secondary amine represented by:

In this case, the IPDI and the sterically hindered secondary amine are 15 to 1, in particular 0.8 to 1, relative to the incyanate group.
It is used in an amount equal to moA (second amine).

For the above reasons, it is not surprising that many blocking agents with active N-, O-, C-hydrogens are not described in the literature as blocking agents for polyisocyanates in powder coatings.

Ureas consisting of mono- and diisocyanates and primary or secondary amines have been used as curing agents for Evoki resins, for example, US Pat. No. 4,222,679; 431
7.612, No. 4521, 549, No. 478-071, No. 4407, 175, No. 8-956, 2
This is clearly indicated by the series of claims set forth in the '57 specification. However, in these cases, curing is essentially effected by reaction of the urea group with the epoxy group to form oxazolidinone. In contrast, ureas consisting of polyicanates and secondary amines as powder hardeners for polyols are not described in the literature. It must be mentioned, of course, that only sterically hindered secondary amines having a boiling point of at least about 160° C. are suitable for preparing the compounds of the invention. Unblocking of IPDI blocked with diisopropylamine can be achieved, for example, with IPDI blocked with caprolactam.
Perform at a lower temperature than However, this product is also not suitable as a PUR powder hardener. This is because the easily volatile amines released during curing form bubbles in the coating.

The more sterically hindered the secondary amine is - to be precise, the steric shielding of the hydrogen atom bonded to 1 - the lower the decomposition temperature of the polyisocyanate blocked thereby.

In general, to prepare the FUR-powder curing agent of the invention, IPDI is reacted in bulk or in solution with a sterically hindered secondary amine without increasing the molecular weight beforehand. In special cases, of course, before blocking IPDI,
It is always advantageous to carry out a reaction to increase the molecular weight using a so-called chain extender, which is customary in incyanate chemistry. In this regard, for example, German Patent Application No. 1.95S 485, German Patent Application No. 2,542,191, German Patent Application No. 4004.876 and German Patent Application No. 2.1O
S, 777 describes chain extension with polyols, and German Patent Application No. 2,7
No. 35,497 and No. λ842.641 describe increasing the molecular weight of IPDI by partial trimerization.

Secondary amines suitable in the present invention corresponding to the above general formula include, for example, tert-butyl-1-methylpentylamine, s-butylbenzylamine, di(1-methylpentyl)-7mine, di(1-methylpentyl)-7mine, -ethylbutyl)-amine, dicyclohexylamine, tert-butyl-cyclohexylamine, di(3,5,5-)limethyl)-cyclohexylamine, dicyclopentylamine, 2.6
-dimethylpiperidine, 45-dimethylmorpholine and their analogs.

Mixtures of these secondary amines may also be used according to the invention.

The reaction between IPDI and the secondary amine can be carried out in a solvent or in the melt. When carried out in bulk, the IPDI K secondary amine heated to 70-120 DEG C. is metered in such that the temperature of the reaction mixture does not rise above 130 DEG C.

After the addition of the blocking agent is complete, the reaction mixture is further heated to about 100 DEG -120 DEG C. for about an additional hour to complete the reaction.

As already mentioned, blocking can also be carried out in a solvent.

As a solvent for this reaction, of course, only those that do not react with IPDI, such as ketones such as acetone, methyl ethyl ketone, methyl-imbutyl ketone, cyclopentanone, cyclohexanone, etc.; aromatic compounds such as toluene, nitrobenzene, etc.; Suitable are ethers, eg evatetrahydrofuran, dioxane; as well as aprotic solvents such as dimethylformamide, dimethylacetamide, dimethylsulfoxide and the like.

In the case of the compounds of the invention thus obtained, generally 3
Compounds in the molecular weight range from 00 to 900, especially from 350 to 700, are of concern. These products are 70-180
℃, especially a melting point range of 80 to 140℃. The secondary amine-blocked IPDI furthermore has a content (calculated as NCO) of incyanate groups terminally present in the blocked state of 8 to 20% by weight, in particular 10
It is also characterized by ~16% by weight.

This product is particularly suitable for Zerwitinof.
f) Suitable as curing agent for polyfunctional compounds with active hydrogen atoms. In combination with compounds with this type of Tzelevitinoff active hydrogen atom, the product has 1
At temperatures above 10 DEG C., in particular from 130 DEG to 170 DEG C., systems are formed which can be cured into expensive synthetic resins. The most important field of application for the compounds of the invention is their use as binders for light-stable polyurethane powder coatings.

The thermosetting powder composition in which the blocked polyisocyanate according to the invention is used contains the following components: a) 100i4i parts of hydroxyl-containing polymer b) 10 to 90 parts
parts by weight of blocked IPDIc) 0 to 120 parts by weight of pigments d) 0 to 201 parts by weight of customary fillers e) 0
~5 parts by weight of catalyst f) 0 to 5 parts by weight of leveling agent component a) are obtained in principle in all polymerizations 1) containing two or more OH groups and melting at at least 70 DEG C.

In this case, polyether polyols, polyester-amide-polyols, polyurethane-polyols, hydroxylated acrylic resins, etc. are suitable, and the OH
The groups are designed to crosslink with blocked IPDI according to the invention. Regarding polymers having hydroxyl groups within the scope of the present invention, polyester-
Particular preference is given to polyols.

The polyester-polyol is 1. O00~10
,000, especially 1.500 to -〇〇〇 molecular weight 2
0-240. In particular, it must have an OH value of 30 to 100(7). Such polyester-polyols are described, for example, in German Patent Applications 1,95,483, 2,542,191, 4004,876, and 3,143,060. ing.

A catalyst may be added to accelerate the gelation rate of the heat-curable composition. As a catalyst, an organic tin compound such as dibutyl-tin-dilaurate, 5n(II)-octoate, dibutyltin maleate, etc. is used.

The amount of the catalyst added is 1 to 5 t% by weight based on 100 parts by weight of the hydroxyl group-containing polymer. The coatings produced according to the invention are distinguished by excellent weather resistance and very good color stability.

Production Example 1 of Blocked Polyisocyanate 444 parts by weight of isophorone diincyanate (IPDI
) Add 724 parts by weight of dicyclohexylamine at 120°C so that the temperature of the reaction mixture does not rise above 130°C. After addition of dicyclohexylamine, further heating is performed at 150° C. for an additional hour to complete the reaction.

The reaction product thus produced has a melting point of 105 DEG -110 DEG C. and a block NCO content of 14.3%.

Example 2 222 parts by weight of IPDI at 130°C 550
Parts by weight of di(5,5-trimethyl)-cyclohexylamine are added over a period of about 2 hours.

After the amine addition was complete, the reaction mixture was heated for an additional 2 hours.
Heat further at 30°C. This reaction mixture is 84~
It has a melting point of 91°C and a block NGO content of 111%.

Example 5 Analogously to the method described in Examples 1 and 2, 222 parts by weight of IPDI are reacted with 226 parts by weight of 2,6-dimethylpiperidine.

This reaction product has a melting point of 99-105°C and 1&7%
It has a block NGO-containing U.

111 dissolved in 500 parts by weight of water-free acetone
Add 10 parts by weight of diisopropylamine to 10 parts by weight of IPDI in a package over a period of about 2 hours. After addition of diisopropylamine, heat at 50° C. for a further 2 hours. Thereafter, the acetone is distilled off and residual acetone is removed in a vacuum drying chamber at 60° C. and 1 Ht. The reaction product has a melting point of 65-74°C and a block NCO content of 19.8%.

Example 5 (Comparative Example) IPDI of the 111 heavy site was performed in the same manner as described in Example 4.
and 129 parts by weight of di-isobutylamine are reacted.

The reaction product has a melting point of 73-77°C and 17.5%
It has a block NCO content of .

Example 6 (comparative example) 444 parts by weight of IPDI VCl 40 at 10°C
Add 0 parts of N-methylbiperazine so that the temperature of the reaction mixture does not rise above 135°C. After the addition of the amine was completed, the temperature was increased to 130°C for an additional hour to complete the reaction.
Heat it further. The reaction product thus produced has a melting point of 75-77°C and a block NC' of 7% la.
It has O content.

Free amines were no longer detected in Examples 1-6.

B. Polyol component General manufacturing recipe Raw material component - Terephthalic acid (T8)? Dimethyl terephthalate (DMT), hexanediol-1°6 (HD)
, neopentyl glycol (NPG), 1,4-diif
cyclohexane (DMC) and trimethylolpropane (TMP) are placed in a reactor and oil
Warm by bath. After most of the material has melted,
At a temperature of 160 DEG C. Q, 0.5% by weight of di-n-butyl tin oxide is added as a catalyst. The first methanol release occurs at a temperature of about 170°C. Temperature 2 for 6-8 hours
The temperature is increased to 20-2SO DEG C. and the reaction is complete after a further 12-15 hours. 50-4 by cooling the polyester to 200 °C and placing it under reduced pressure (1ymHf)
Volatile components are thoroughly removed during 5 minutes. During the entire reaction time, the distillate is stirred and a weak N,- flow is passed through the reaction mixture.

The following table shows the composition of the polyesters and the corresponding physical and chemical data.

C. Polyurethane - Powder Coating General Preparation Recipe The ground product, crosslinking agent, polyester, leveling agent, masterbatch are thoroughly mixed together with optional white pigment and optionally filler in a wheel mill. Then, it is homogenized in an extruder at 80-110°C. After cooling, the extrudate is crushed and crushed in a crusher with pins.
Grind to a particle size of 0 pm. The powder thus produced is applied in an electrostatic powder spraying device under 60 KV to degreased and optionally pretreated steel sheets and baked in a drying chamber with air circulation.

Leveling agent masterbatch 10% by weight leveling agent - butyl acrylate and 2-
A commercially available copolymer with ethylhedyl acrylate is homogenized in the molten state in the corresponding polyester and, after solidification, is ground.

The following abbreviations in the tables below have the following meanings: SD = layer thickness μrn), HK = K”onig hardness (sec) (D
IN5 to 157), HB = Buchholz hardness (DIN 5!% 15 S), g'I' =
Erichsen test value (w) (DIN S!1,156)
, ()S = cross-cut test value (DIN 5 to 15
1), () () 60' (= Gardner (Cardnet
) Gloss measurements (A8TM-D52S) Example 1 A powder coating of the following formulation is prepared according to the above method, applied and baked at 160-200C.

48? , 4 parts by weight of the polyester 17G of Example 8.1
, 6 parts by weight of Example 1 crosslinking agent 48α 0 parts by weight of white pigment (Tie, ) b a o i
t t Part o Rehelling Agent - Masterbatch Example 2 Pigmented Coating A powder coating of the following formulation is prepared according to the above method, applied and baked at 160-200°C.

4558 parts by weight of example B, 1 part of polyester 2062 weight part 2 part of crosslinking agent 48 (10 parts by weight of white pigment (6αo weights)
Leveling agent - Masterbatch Example 3 A powder coating of the following formulation is prepared according to the above method, applied and baked at 160-200C.

Example B of 2 parts by weight of 42α, 2 polyester 129,8
Examples of parts by weight A, 1 part cross-linking agent 400, 0 parts by weight white pigment (T i 02 ) sIln heavy parts leveling agent -
Masterbatch Example 4 A powder coating of the following formulation is prepared according to the above method, applied and baked at 160-200°C.

592.2i Tanbe example B, 2 polyester 157,
8 parts of cross-linking agent 2 parts by weight, 0 parts by weight of white pigment (T102) 50.0 parts by weight
Part Leveling Agent - Master Bunch Example 5 (Comparative Example) A powder coating of the following formulation is prepared according to the above method, applied and baked at 160-200°C.

525, 1 part by weight Example B, 1 Polyester 134,
9 parts by weight of example 4 crosslinking agent 48G, 0 parts by weight of white pigment (Tiot) 6αo weight i
Part Leveling Agent - Master Bunch Sample If the coating thickness is >40 μm, a problem-free coating surface cannot be obtained. There is significant foam formation.

A powder coating of the following formulation is prepared according to the above method, applied and baked at 160-200°C.

519, 0 parts by weight Example B, 1 polyester 141,
0 parts by weight of example 1 crosslinking agent 4aaOjLf 1 part of white pigment (TiO2) AaOff
It was not possible to ascertain the properties of the paint due to the significant foam formation of the 411 pyr thick coating.

Claims (1)

[Claims] A storage-stable polyurethane resin powder coating that cures at 170°C or less and is composed of a polyol and blocked isophorone diisocyanate (IPDI),
A general formula with a boiling point of at least 150℃ ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [In the formula, R and R' are an alkyl group - this alkyl group is N
are mutually the same or different substituents from the group of -, optionally substituted cycloalkyl, aralkyl groups, which are always substituted in the α-position, and R and R' in total are at least 9 carbon atoms and optionally R and R' may form a common ring with at least 3 carbon atoms, these carbon atoms optionally being heterogeneous. Interrupted and optionally substituted by atoms (N, O). ] The second -
The above-mentioned polyurethane resin powder coating, which is characterized by reacting with an amine.